A post-earthquake traffic system function loss evaluation method based on road width

Abstract

The application relates to a post-earthquake traffic system function loss evaluation method based on road width and belongs to the field of earthquake engineering. The application is to solve the problem that the analysis method of emergency connectivity in the existing post-earthquake traffic system operation function evaluation cannot judge the seismic resilience level of the traffic system. The post-earthquake traffic system function loss evaluation method based on road width is characterized in that: firstly, redundant independent paths between each starting node and each target node in the pre-earthquake path network are removed, and the remaining independent paths are searched; then, the function loss of the post-earthquake emergency stage path network is analyzed to update the width, length and number of each road section in the post-earthquake path network, the independent paths are searched again, and the path information of each independent path after the earthquake is obtained; finally, the emergency function indexes of the pre-earthquake and post-earthquake urban road traffic systems are calculated by using the path information of each independent path before and after the earthquake, and then the function loss of the urban road traffic system in the post-earthquake emergency stage is calculated and obtained.

Description

Technical Field

[0001] This invention belongs to the field of earthquake engineering, and in particular relates to the evaluation of urban traffic conditions after an earthquake. Background Technology

[0002] Earthquakes are among the most devastating natural disasters affecting people's daily lives, with an average of over 10,000 earthquakes occurring daily worldwide. Since 2003, various countries have successively proposed plans and goals for urban earthquake resilience to reduce post-disaster losses. With the continuous growth of the population, increasingly dense buildings, and the proliferation of complex bridges within cities, the transportation system, as one of the most important urban infrastructure systems, bears the most urgent responsibility for rescue and relief efforts after an earthquake. If the transportation system suffers minimal functional loss, rescue and relief work can proceed smoothly and effectively; however, if large-scale collapse of buildings along streets and extensive damage to complex bridges reduce the remaining width of roads and impair the connectivity of the entire road network, the transportation system will be severely damaged or even collapse, leading to even more severe economic and social losses and greater casualties, ultimately paralyzing the entire city.

[0003] Urban road traffic systems are crucial for ensuring the flow of urban resources after an earthquake. Unlike other lifeline systems, the post-earthquake availability of road traffic systems cannot be quantified by the number of users served. Instead, it requires complex modeling and functional analysis to reflect the system's true operational status. Unlike daily traffic, people's traffic behavior undergoes fundamental changes after an earthquake. Among existing methods for assessing the overall operational function of urban road traffic systems, connectivity and traffic flow methods are the most widely used, each with its own characteristics: connectivity methods are typically used for studying emergency traffic functions after an earthquake, while traffic flow methods are more suitable for studying long-term post-earthquake functions. However, existing emergency connectivity analysis methods do not consider the emergency functional attributes of starting and destination nodes in the road network, nor the contribution of the dual redundancy of emergency facilities and network paths to the emergency function of the road traffic system. Furthermore, they cannot quantify the impact of traffic components under various damage states on the system's post-earthquake connectivity, thus failing to predict and estimate the extent of the traffic system's ability to withstand disasters after an earthquake, i.e., they cannot determine the level of seismic resilience of the traffic system.

[0004] Currently, the resilience of urban road transportation systems is crucial for the sustainable development of modern cities. The connectivity of the road network during the post-earthquake emergency phase directly affects the magnitude of urban post-earthquake losses and the recovery time. Therefore, it is essential to develop a method for evaluating the functional losses of post-earthquake transportation systems during the emergency phase, taking into account building collapse and bridge damage. Summary of the Invention

[0005] This invention addresses the problem that existing methods for assessing the operational function of urban post-earthquake transportation systems cannot determine the seismic resilience level of the transportation system. It provides a method for evaluating the functional loss of post-earthquake transportation systems based on road width.

[0006] A method for evaluating the functional loss of a post-earthquake transportation system based on road width includes:

[0007] Redundant independent paths between each starting node and each target node in the pre-earthquake path network are removed, and the remaining independent paths are searched to obtain the path information of each pre-earthquake independent path. The path information includes the number, length, and width of the road segments passed through in the independent path, as well as the order and number of the nodes passed through.

[0008] The functional loss of the post-earthquake emergency path network is analyzed to update the width, length and number of each road segment in the post-earthquake path network. Redundant independent paths between each starting node and each target node in the post-earthquake path network are removed and the remaining independent paths are searched to obtain the path information of each independent path after the earthquake.

[0009] By using the path information of each independent path before and after the earthquake, the emergency function indicators of the urban road traffic system before and after the earthquake are calculated, and then the functional loss of the urban road traffic system in the emergency phase after the earthquake is calculated.

[0010] Furthermore, the remaining independent paths between each starting node and each target node in the path network are searched to obtain the path information of each independent path, including:

[0011] S1: Consider a starting node to a target node as a single target, and construct a target set. The total number of targets in the target set is Q, where q = 1, 2, ..., Q.

[0012] S2: Search for the independent path with the highest road segment efficiency among all independent paths between the starting node and the target node of the q-th target, record the path information of the independent path, and delete all road segments contained in the independent path;

[0013] S3: Determine whether there is an independent path between the starting node and the target node of the q-th target. If yes, return to S2; otherwise, execute S4.

[0014] S4: Determine if q = Q. If yes, end the path search; otherwise, restore all segments in the path network to make q = q + 1, and then return to S2.

[0015] The expression for the traffic efficiency of the road segment is as follows:

[0016]

[0017] Where h(i) is the traffic efficiency of the i-th road segment, l i and w i Let be the length and width of the i-th road segment, respectively, and M be the total number of road segments contained in an independent path.

[0018] Furthermore, the functional loss of the route network during the post-earthquake emergency phase is analyzed to update the width, length, and numbering of each route segment in the post-earthquake route network, including:

[0019] The number of remaining effective lanes on each road segment after the earthquake was obtained based on the impact analysis of buildings and bridges on the traffic system, and the nominal length of each road segment after bonuses was calculated.

[0020] The nominal lengths of each road segment after the reward are used to update the nodes, widths, lengths, and numbers of each road segment in the post-earthquake path network.

[0021] Furthermore, the nominal length of each road segment after the bonus is calculated, including:

[0022] Calculate the width reward factor for each road segment:

[0023]

[0024] Where, γ i N is the width reward factor for the i-th road segment. i_post Let i be the number of valid lanes remaining on the i-th road segment after the earthquake.

[0025] Calculate the nominal length of each road segment after bonus based on the width bonus factor for each segment:

[0026] l i ′=l i ×γ i ,

[0027] Among them, l i ′ is the nominal length of the i-th road segment after the bonus, l i Let be the actual length of the i-th road segment.

[0028] Furthermore, the number of remaining effective lanes N for the i-th road segment after the earthquake. i_post The expression is:

[0029]

[0030] in, W indicates rounding down. remain This represents the remaining effective width of the road section after the earthquake.

[0031] Furthermore, using the route information of each independent path before and after the earthquake, the emergency function indicators of the urban road traffic system before and after the earthquake were calculated, including:

[0032] Calculate the sum of the travel efficiencies of the independent paths between the starting node and the target node to obtain the emergency connectivity performance index:

[0033]

[0034] in, For the v-th starting node and the target node set E t Emergency connectivity indicators between the j-th target nodes and The v-th starting node and the target node set E are respectively. t The length and width of the k-th independent path between the j-th target nodes. For the v-th starting node and the target node set E t The total number of independent paths between the j-th target node;

[0035] Calculate the overall connectivity indicators for various emergency services using emergency connectivity indicators:

[0036]

[0037] In the formula, For the overall connectivity indicators of the t-th type of emergency service, For the v-th starting node to the target node set E t The traffic demand weight of the j-th target node;

[0038] By weighting the overall connectivity indicators of different categories of emergency services, the emergency function indicators of the urban road traffic system are obtained:

[0039]

[0040] Among them, F E For the emergency response function indicators of the urban road traffic system, T represents the total number of emergency service categories; J represents the total number of target nodes in a certain type of target node set. For the set of target nodes of class t, E t The emergency response capability weight of the j-th target node.

[0041] Furthermore, the v-th starting node is paired with the target node set E. t Traffic demand weight of the j-th target node The expression is:

[0042]

[0043] in, Represents the v-th starting node to the target node set E. t The demand state of the j-th target node, when there is demand The value is 1 if it is not 0 otherwise.

[0044] For the v-th starting node to the target node set E t The demand weight of the j-th target node, and satisfying n is the total number of starting nodes.

[0045] Furthermore, the set of target nodes of class t, E t Emergency response capability weight of the j-th target node The expression is:

[0046]

[0047] in, For the set of target nodes of class t, E t The emergency response capability of the j-th target node. For the set of target nodes of class t, E t The maximum emergency response capability in the country.

[0048] Furthermore, when the emergency service category is command service, the emergency capability weight is 1;

[0049] When the emergency service category is medical rescue service, the formula for calculating the emergency response capacity weight is as follows:

[0050]

[0051] HTC represents the rescue capacity weight of the j-th medical rescue center. j To enhance the treatment capacity of the j-th medical rescue center, HTC max To maximize treatment capacity;

[0052] When the emergency service category is shelter and resettlement service, the formula for calculating the emergency response capacity weight is as follows:

[0053]

[0054] Let RDAS be the refuge capacity weight of the j-th refuge center. j For the effective disaster tolerance area of ​​the j-th evacuation and resettlement center, RDAS max To maximize the effective disaster recovery area;

[0055] When the emergency service category is fire and rescue service, the formula for calculating the emergency response capability weight is as follows:

[0056]

[0057] Let FSVN be the rescue capability weight of the j-th fire and rescue center.j Let FSVN be the number of vehicles on duty at the j-th fire and rescue center. max This represents the maximum number of vehicles allowed on duty.

[0058] When the emergency service category is material support service, the formula for calculating the emergency capability weight is as follows:

[0059]

[0060] RSL represents the support capacity weight of the j-th material support center. j Let RSL be the area of ​​the j-th material support center. max This is the largest area of ​​the material support center.

[0061] Furthermore, the functional losses of the urban road traffic system during the post-earthquake emergency phase are calculated, including:

[0062]

[0063] Among them, FS CE For the functional loss of the urban road traffic system during the post-earthquake emergency phase, F E (tpre) and F E (tpost) represents the emergency function indicators of the urban road traffic system before and after the earthquake, respectively.

[0064] The beneficial effects of the post-earthquake traffic system functional loss evaluation method based on road width described in this invention are as follows:

[0065] 1. Roads and bridges constitute the most important transportation routes in a city at any time, playing a crucial role in emergency rescue and relief work in the initial stages of an earthquake. Post-earthquake rescue and relief work correspond to the starting points of different emergency functional attributes within the urban road network. This invention can search for multi-destination independent paths between nodes and sets of emergency facilities in the chaotic post-earthquake scenario, based on the needs of different starting and ending points.

[0066] 2. This invention assigns different weights to different target nodes, which can better reflect the capability level of different target nodes, thereby allocating resources according to their different capabilities and maximizing the efficiency of post-earthquake rescue and relief.

[0067] 3. Due to the significant difference in residents' travel needs before and after the earthquake, an emergency function index applicable to the road traffic system is proposed to quantify the contribution of redundancy in emergency facilities and routes, providing support for assessing the seismic resilience of urban transportation systems.

[0068] 4. A method for assessing post-earthquake functional loss based on a width reward factor was constructed. This method can quantify the level of urban functional reduction after an earthquake, thereby determining the city's ability to withstand disasters during the post-earthquake emergency period and thus ensuring the minimization of risk losses.

[0069] In summary, this invention relates to the evaluation of the seismic resilience of urban transportation systems in the field of earthquake engineering, and is particularly applicable to the evaluation of the functional loss of transportation systems caused by the collapse of street-facing buildings and bridge damage during the post-earthquake emergency period. Attached Figure Description

[0070] Figure 1 This is a route relationship diagram between emergency nodes and ordinary nodes in the road network during the post-earthquake emergency period;

[0071] Figure 2 Here is a flowchart of the path search algorithm;

[0072] Figure 3 The impact of post-earthquake building collapses on the functional loss of urban transportation systems;

[0073] Figure 4 This refers to the impact of bridge damage on the functionality of urban transportation systems after an earthquake. Detailed Implementation

[0074] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0075] Reference Figures 1 to 4 This embodiment specifically describes a method for evaluating the functional loss of a post-earthquake transportation system based on road width, including:

[0076] Step 1: Clarify the classification of emergency nodes in the post-earthquake emergency response network.

[0077] Rescue and relief are the two most urgent and crucial tasks for a city after a disaster. Due to the different functions of emergency facilities within a city after a disaster, emergency services in the road network can be broadly categorized into five types: command services, medical rescue services, fire rescue services, material support services, and shelter and resettlement services. Each type of emergency service is provided through multiple emergency nodes, namely: command center, medical rescue center, fire rescue center, material support center, and shelter and resettlement center. The command center is the location where city decision-makers issue instructions and monitor and coordinate the entire emergency response after the disaster, such as the government. The medical rescue center refers to a location within the city with a certain level of medical treatment capacity that can provide medical assistance to injured residents after the disaster, such as a tertiary hospital or a temporary makeshift hospital. The fire rescue center is considered the initial location for responding to the city's decision-makers' instructions after the disaster, such as fire brigades or police stations. The material support center is the starting point for storing and transporting supplies within the city after the disaster, such as large supermarkets or train stations. Disaster relief centers are temporary shelters within cities after an earthquake, providing large open spaces for affected residents, such as parks and stadiums. In the post-earthquake emergency road network, the relationship between the start and end points of these emergency nodes and ordinary nodes is as follows: Figure 1 As shown.

[0078] Throughout the emergency response phase following an earthquake, the relationships of traffic behavior within the road network are as follows: Figure 1 As shown, government commanders (command center) issue rescue orders to various fire and rescue centers throughout the city, assigning them to nearby disaster-stricken areas to rescue victims. Firefighters gather information about the situation in the affected areas and relay it back to the command center. After unified dispatch by the command center, some vehicles transport the injured to hospitals (medical rescue centers), while others evacuate the affected population to open areas within the city (evacuation and resettlement centers) to prevent their lives from being threatened. Simultaneously, the command center dispatches additional vehicles from supply depots (supply centers) to deliver relief supplies to the evacuation and resettlement centers to ensure the evacuees have access to food and shelter.

[0079] Step 2: Define the emergency response capability weights of emergency nodes.

[0080] Due to urban planning requirements, different emergency response nodes of the same type may have varying service functions and capabilities. To better reflect these differences, different weights need to be assigned based on their characteristics. The command center contains numerous urban remote monitoring and control devices, thus it has a high safety margin during the design phase. It is assumed that the command center will not suffer moderate or greater damage after an earthquake, therefore its weight is 1. The emergency response capability weights of each emergency response node (medical rescue center, fire rescue center, material support center, and shelter center) are calculated using the following formula:

[0081]

[0082] in, For the set of target nodes of class t, E t The emergency response capability weight of the j-th target node. For the set of target nodes of class t, E t The emergency response capability of the j-th target node. For the set of target nodes of class t, E t The maximum emergency response capability.

[0083] The specific formula for calculating the weight of each type of emergency node (target node) is as follows:

[0084] When the emergency service category is medical rescue service, the formula for calculating the emergency response capacity weight is as follows:

[0085]

[0086] HTC represents the rescue capacity weight of the j-th medical rescue center. j To enhance the treatment capacity of the j-th medical rescue center, HTC max To maximize treatment capacity.

[0087] When the emergency service category is shelter and resettlement service, the formula for calculating the emergency response capacity weight is as follows:

[0088]

[0089] Let RDAS be the refuge capacity weight of the j-th refuge center. j For the effective disaster tolerance area of ​​the j-th evacuation center, according to the "Regulations on Urban Green Space Planning and Construction Indicators," the actual usable area for evacuation in parks and green spaces is generally calculated using a standard ratio of 60% to 70%. RDAS max This is the maximum effective disaster recovery area.

[0090] When the emergency service category is fire and rescue service, the formula for calculating the emergency response capability weight is as follows:

[0091]

[0092] Let FSVN be the rescue capability weight of the j-th fire and rescue center. j Let FSVN be the number of vehicles on duty at the j-th fire and rescue center. max This represents the maximum number of vehicles allowed on duty.

[0093] When the emergency service category is material support service, the formula for calculating the emergency capability weight is as follows:

[0094]

[0095] RSL represents the support capacity weight of the j-th material support center. j Let RSL be the area of ​​the j-th material support center. max This is the largest area of ​​the material support center.

[0096] Step 3: Path search.

[0097] Given the start and end points in the path network, the next step is to determine the path information between them. This implementation improves upon the independent path search method based on a single start and end point, making it suitable for multi-destination independent path search considering segment width between a starting node and a set containing multiple target nodes. Figure 2 As shown, the specific steps include:

[0098] S1: Treat a starting node to a target node as a target and construct a target set, where the total number of targets in the target set is Q, q = 1, 2, ..., Q.

[0099] S2: Search for the independent path with the highest traffic efficiency among all independent paths between the starting node and the target node of the q-th target, record the path information of the independent path, and delete all road segments contained in the independent path.

[0100] The expression for the traffic efficiency of the road segment is as follows:

[0101]

[0102] Where h(i) is the traffic efficiency of the i-th road segment, l i and w i Let be the length and width of the i-th road segment, respectively, and M be the total number of road segments contained in an independent path.

[0103] S3: Determine whether there is an independent path between the starting node and the target node of the q-th target. If yes, return to S2; otherwise, execute S4.

[0104] S4: Determine if q = Q. If yes, end the path search; otherwise, restore all segments in the path network so that q = q + 1, and then return to S2.

[0105] Step 4: Functional loss analysis during the post-earthquake emergency phase.

[0106] Earthquakes can cause the collapse of numerous frame, masonry, and base-frame structures along streets, and the resulting rubble can impact the surrounding roads. Currently, bridges within cities serve to distribute some traffic flow, often existing as "bridges above roads." Earthquakes also damage bridges within the transportation network, affecting its connectivity. Specific impacts of buildings and bridges on the transportation system include... Figure 3 and Figure 4 .

[0107] Post-earthquake emergency route search is based on the existence of a route, which cannot quantify the impact of damaged road sections that can still be used by transport vehicles. Therefore, a width reward factor is proposed to consider the impact of road sections under different damage states on the function of the road traffic system. Traffic congestion and reduced traffic speed caused by the functional impairment of road sections after an earthquake will ultimately be reflected in the longer travel time required to traverse those sections compared to normal conditions, which is equivalent to a longer journey for users. Conversely, road sections with less damage or no damage are equivalent to a shorter journey.

[0108] Considering the impact of building collapse and bridge damage on the remaining width of corresponding road sections, the reciprocal of the number of remaining effective lanes after the earthquake is defined as the width bonus factor for the road section:

[0109]

[0110] Where, γ i N is the width reward factor for the i-th road segment. i_post Let be the number of valid lanes remaining in the i-th road segment after the earthquake, and we have:

[0111]

[0112] W indicates rounding down. remain This represents the remaining effective width of the road section after the earthquake.

[0113] The nominal length of the road segment after the bonus is:

[0114] l i ′=l i ×γ i ,

[0115] In the formula, l i ′ is the nominal length of the i-th road segment after the bonus, l i Let be the actual length of the i-th road segment.

[0116] Finally, the nominal lengths and numbers of road segments in the post-earthquake path network are updated using the road segment reward. Then, the method described in step three is used again to search for paths in the post-earthquake path network, and the numbers, lengths, and widths of all road segments contained in each independent post-earthquake path are recorded.

[0117] Step 5: Determine emergency function indicators.

[0118] The assessment of the emergency connectivity function of an urban road system depends primarily on two factors:

[0119] 1. The more independent paths there are between the starting node and the target node set, the stronger the temporary response capability and the stronger the emergency connectivity function when the road network is blocked due to uncertainty.

[0120] 2. The traffic efficiency of each route depends on the length and width of each route that makes up the road segment. The shorter the length and the wider the width, the higher the efficiency and the stronger the emergency connectivity function.

[0121] Therefore, the sum of the passage efficiencies of the independent paths between the starting node and the target node is defined as the emergency connectivity function index:

[0122]

[0123] In the formula, where, For the v-th starting node and the target node set E t Emergency connectivity indicators between the j-th target nodes; and The v-th starting node and the target node set E are respectively. t The length and width of the k-th independent path between the j-th target nodes are given, and the overall width of the path is the average width of all road segments traversed by the path. For the v-th starting node and the target node set E t The total number of independent paths between the j-th target node.

[0124] The sum of the products of the supply capacity of the target node set to all nodes in the path network and their corresponding traffic demand weights is defined as the overall connectivity index of a certain type of emergency service in the path network:

[0125]

[0126] In the formula, For the overall connectivity indicators of the t-th type of emergency service, For the v-th starting node to the target node set E t The traffic demand weight of the j-th target node is given, and we have:

[0127]

[0128] Represents the v-th starting node to the target node set E. t The demand state of the j-th target node, when there is demand The value is 1 if it is set to 1, and 0 otherwise. For the v-th starting node to the target node set E t The demand weight of the j-th target node is determined based on the city's internal population heat map and satisfies the following conditions: n is the total number of starting nodes.

[0129] Finally, the connectivity of different categories of emergency services is weighted and defined as a comprehensive emergency function index of the city's road system:

[0130]

[0131] In the formula, F E For the emergency response function indicators of the urban road traffic system, T represents the total number of emergency service categories; J represents the total number of target nodes in a certain type of target node set. For the set of target nodes of class t, E t The emergency response capability weight of the j-th target node.

[0132] Calculate the emergency functional indicators before and after the earthquake using the steps described above. Then, calculate the functional loss of the urban road traffic system during the emergency phase after the earthquake using the following formula:

[0133]

[0134] Among them, FS CE For the functional loss of the urban road traffic system during the post-earthquake emergency phase, F E (tpre) represents the pre-earthquake emergency function index of the urban road traffic system, F E (t post () refers to the emergency function indicators of the urban road traffic system after an earthquake.

[0135] While the invention has been described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the invention. Therefore, it should be understood that many modifications can be made to the exemplary embodiments, and other arrangements can be designed without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that different dependent claims and features described herein can be combined in ways different from those described in the original claims. It is also understood that features described in conjunction with individual embodiments can be used in other described embodiments.

Claims

1. A method for evaluating the functional loss of a post-earthquake transportation system based on road width, characterized in that, include: Redundant independent paths between each starting node and each target node in the pre-earthquake path network are removed, and the remaining independent paths are searched to obtain the path information of each pre-earthquake independent path. The path information includes the number, length, and width of the road segments passed through in the independent path, as well as the order and number of the nodes passed through. The functional loss of the post-earthquake emergency path network is analyzed to update the width, length and number of each road segment in the post-earthquake path network. Redundant independent paths between each starting node and each target node in the post-earthquake path network are removed and the remaining independent paths are searched to obtain the path information of each independent path after the earthquake. Using the path information of each independent path before and after the earthquake, the emergency function indicators of the urban road traffic system before and after the earthquake are calculated, and then the functional loss of the urban road traffic system in the emergency phase after the earthquake is calculated. The analysis of the functional loss of the post-earthquake emergency route network to update the width, length, and numbering of each route segment in the post-earthquake route network includes: The number of remaining effective lanes on each road segment after the earthquake was obtained based on the impact analysis of buildings and bridges on the traffic system, and the nominal length of each road segment after bonuses was calculated. The length and number of each segment in the post-earthquake path network are updated using the nominal length after the reward for each segment; The calculation of the nominal length after the bonus for each road segment includes: Calculate the width reward factor for each road segment: ， in, For the first The width reward factor for each road segment. For the first The number of remaining effective lanes on this road section after the earthquake. Calculate the nominal length of each road segment after bonus based on the width bonus factor for each segment: ， in, For the first The nominal length of the road segment after the bonus, For the first The actual length of the road segment; The first The number of remaining effective lanes on this road section after the earthquake The expression is: ， in, Indicates rounding down. This represents the remaining effective width of the road section after the earthquake.

2. The method for evaluating the functional loss of a post-earthquake transportation system based on road width according to claim 1, characterized in that, Search for the remaining independent paths between each starting node and each destination node in the path network to obtain the path information of each independent path, including: S1: Treat a starting node to a target node as a single target, construct a target set, and the total number of targets in the target set is... , ; S2: In the Search for the independent path with the highest traffic efficiency among all independent paths between the starting node and the target node, record the path information of the independent path, and delete all road segments contained in the independent path. S3: Determine the first If there is an independent path between the starting node and the target node of each target, return to S2; otherwise, execute S4. S4: Determine if If yes, end the path search; otherwise, restore all road segments in the path network, so that... Then return to S2; The expression for the traffic efficiency of the road segment is as follows: ， in, For the first Traffic efficiency of this road section and The first The length and width of the road segment This represents the total number of road segments contained in an independent path.

3. A method for evaluating the functional loss of a post-earthquake transportation system based on road width, as described in claim 1 or 2, characterized in that, The calculation of emergency function indicators of the urban road traffic system before and after the earthquake, using path information from each independent path before and after the earthquake, includes: Calculate the sum of the travel efficiencies of the independent paths between the starting node and the target node to obtain the emergency connectivity performance index: ， in, For the first A set of starting nodes and target nodes The Middle Emergency connectivity indicators between target nodes and The first A set of starting nodes and target nodes The Middle Between the nth target nodes The length and width of each independent path, For the first A set of starting nodes and target nodes The Middle The total number of independent paths between target nodes; Calculate the overall connectivity indicators for various emergency services using emergency connectivity indicators: ， In the formula, For the first Overall connectivity metrics for emergency services. For the first A set of starting nodes and target nodes The Middle Traffic demand weights for each target node; By weighting the overall connectivity indicators of different categories of emergency services, the emergency function indicators of the urban road traffic system are obtained: ， in, For emergency function indicators of urban road traffic systems, The total number of emergency service categories. The total number of target nodes in a certain type of target node set. For the first Class target node set The Middle Emergency response capability weights for each target node.

4. The method for evaluating the functional loss of a post-earthquake transportation system based on road width according to claim 3, characterized in that, The first A set of starting nodes and target nodes The Middle Traffic demand weights for each target node The expression is: ， in, Indicates the first A set of starting nodes and target nodes The Middle The demand status of each target node, when there is demand. The value is 1 if it is set to 1, and 0 otherwise. For the first A set of starting nodes and target nodes The Middle The required weights of each target node, and satisfying , This represents the total number of starting nodes.

5. The method for evaluating the functional loss of a post-earthquake traffic system based on road width according to claim 4, characterized in that, The first Class target node set The Middle Emergency response capability weight of each target node The expression is: ， in, For the first Class target node set The Middle Emergency response capabilities of each target node For the first Class target node set The maximum emergency response capability in the country.

6. The method for evaluating the functional loss of a post-earthquake traffic system based on road width according to claim 5, characterized in that, When the emergency service category is command service, the emergency capability weight is 1. When the emergency service category is medical rescue service, the formula for calculating the emergency response capacity weight is as follows: ， For the first Weighting of the rescue capabilities of each medical rescue center For the first The treatment capacity of each medical rescue center To maximize treatment capacity; When the emergency service category is shelter and resettlement service, the formula for calculating the emergency response capacity weight is as follows: ， For the first The refuge capacity weight of each refugee center For the first The effective disaster tolerance area of ​​each refuge and resettlement center To maximize the effective disaster recovery area; When the emergency service category is fire and rescue service, the formula for calculating the emergency response capability weight is as follows: ， For the first The rescue capability weight of each fire and rescue center For the first The number of vehicles on duty at each fire and rescue center This represents the maximum number of vehicles on duty. When the emergency service category is material support service, the formula for calculating the emergency capability weight is as follows: ， For the first Weighting of the support capacity of each material support center For the first The area of ​​each material support center This is the largest area of ​​the material support center.

7. The method for evaluating the functional loss of a post-earthquake transportation system based on road width according to claim 3, characterized in that, The calculation yields the functional losses of the urban road traffic system during the post-earthquake emergency phase, including: ， in, The functional loss of the urban road traffic system during the post-earthquake emergency phase. and These are the emergency function indicators of the urban road traffic system before and after the earthquake.

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